1.6 billion stars. 11.4 million galaxies. 158,000 asteroids.
Launched in 2013 by the European Space Agency’s Gaia Space Observatory, it has long since exceeded its goal of drawing more than a billion stars in the Milky Way (SN: 15.10.16). On June 13, the mission expanded this map into new dimensions, releasing more detailed measurements of hundreds of millions of stars, plus – for the first time – asteroids, galaxies and dusty interstellar environments.
“Suddenly you have a flow of data,” said Laurent Ayer, an astrophysicist at the University of Geneva who has worked on Gaia for years. For some astronomy topics, the new results effectively replace all previous observations, Ayer said. “The data is better. It’s amazing. “
Data from the new study, collected from 2014 to 2017, already lead to some findings – including the presence of surprisingly massive “star tremors” on the surfaces of thousands of stars (SN: 8/2/19). But most of all, the publication is a new tool for astronomers that will help their efforts understand how stars, planets and entire galaxies form and evolve.
Here are some of the long-running puzzles that data can help solve.
The asteroid belt between Mars and Jupiter is a mess in history. After the formation of the Earth and the other planets, the rocky building blocks that had remained shattered into each other, leaving behind scattered fragments. But if scientists know enough about individual asteroids, they can reconstruct when and where they came from. (SN: 4/13/19). And this can give a glimpse into the earliest days of the solar system.
Gaia’s vast new data set could help solve this puzzle, says Federica Spoto, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. It includes data on the chemical composition of more than 60,000 asteroids – six times more than researchers had before using other instruments. This information can be essential for tracing asteroids back to their shaky origins.
“You can go back in time and try to understand the whole formation and evolution of the solar system,” said Spoto, a Gaia contributor. “This is something huge that we couldn’t even think of before Gaia.
However, asteroids are not just pieces of the past; they are also dangerous. New data could reveal asteroids that are almost impossible to spot from Earth because they orbit too close to the sun, said Thomas Burbin, a planetary scientist at Mount Holyoke College in South Hadley, Massachusetts, who is not on the mission. (SN: 15.02.20). Since these asteroids would initially come from farther away (say, from the asteroid belt), they can tell us about rocks passing by Earth that could potentially hit us. “We’ll get to know our neighborhood better,” says Burbin.
Meeting a star
It is known that it is difficult to measure the age of stars (SN: 23.7.21). “It’s not uncommon to have uncertainty for more than a billion years,” said Alessandro Savino, an astrophysicist at the University of California, Berkeley, who is not affiliated with Gaia. Unlike brightness or location, age is not directly visible. Astronomers must rely on theories of star development to predict age from what they can measure.
If previous versions of the Gaia study were like a picture of stars, the new version is like moving the picture from black and white to color. It provides a deeper look at hundreds of millions of stars by measuring their temperature, gravity and chemistry. “Imagine a star like this point in space, but then they have so many properties,” says Spoto. “That’s what Gaia gives you.”
Although these types of measurements are far from new, they have never been collected in the Milky Way on such a scale. These data could give a better idea of how stars develop. “We can improve the resolution of our watches,” says Savino.
Milky Way snacks
Although it may seem unchanged, the Milky Way is actually fed by a constant diet of smaller galaxies – it is currently even in the process of eating one. But for decades, predictions about when and how these cosmic mergers have been at odds with evidence from our galaxy, said Bertrand Goldman, an astrophysicist at the International Space University in Strasbourg, France, who was not involved in publishing Gaia’s data. “It’s been controversial for a long time,” Goldman said, “but I think Gaia will certainly shed light.”
The key is to be able to separate different structures in the Milky Way and see how old they are (SN: 1/10/20). The latest version of Gaia helps in two ways: by mapping the chemistry of stars and by measuring their motion. Previous versions of the study described how millions of stars move, but mostly in two dimensions. The new catalog quadruples the number of stars with full 3-D trajectories from 7 million to 33 million.
This has implications beyond our neighborhood. Most of the mass in the universe is contained in galaxies like the Milky Way, so knowing how our own galaxy works is a long way to understanding space on a large scale. And the more scientists understand the parts of the galaxy they can see, the more they can learn about dark matter, the mysterious substance that exerts gravity but does not interact with light (SN: 25.06.21).
Even as astronomers dig up this latest set of data, they are already looking forward to future treasure hunts. The next round is in a few years, but is expected to allow the discovery of thousands of exoplanets, produce rare measurements of black holes and help astronomers monitor how fast the universe is expanding. This is partly because Gaia is designed to track the movement of objects in space, and it becomes easier over time. So Gaia’s observations can only become more powerful. “Like good wine, they mature very, very well,” says Savino.